I normally try to save “sloppy slurry”of yeast, in cleaned and sanitized jars. Try to fill the containers as full as possible to reduce potential for oxidization. It works pretty well. Sometimes great. Have had some occasions when making Yeast starter that it did not smell “right” and chose to throw it out rather than risk contamination of brew...

Too bad that you lost an entire batch of beer... Lesson learned, I guess.

Hopefully some of this article will help? I've never done slants, is that freezer dependent? If you go refrigerator route maybe some points on this article will be useful, especially point #5 and the fact that the yeast have something to slowly chump on until the next brew day.

Scott, I've harvested yeast and stored it in glass jars turned upside down to prevent air getting in them. It also worked quite well but I would not store them for more than 3 weeks. (use in two weeks is better)

Mad-Scientist, The slants were kept in the chiller. I've also tried to freeze the yeast in a solution of Agar Agar. I followed the instructions to the letter and it was all a disaster.

I won't be storing yeast in slants or freezing it anymore.

It was a double batch I had to throw away = 46 Litres = 12.15 US Gallons

FYI - I have stored sloppy slurry and reconstituted up to 1-year. Used multiple yeast starters. It worked in at least one case. Frequently save in 3-6 month timeframe, multiple times. Normally works with using yeast starters. Occasionally problems where something doesn’t seem right and I discard and start over with fresh yeast.